(Xojo Plugin) Streaming Encryption

Encrypt and decrypt using a stream.

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Dim crypt As New Chilkat.Crypt2

// Setup encryption using the chacha20 algorithm...
crypt.CryptAlgorithm = "chacha20"
crypt.KeyLength = 256
crypt.EncodingMode = "hex"
Dim ivHex As String
ivHex = "000000000000000000000002"
crypt.SetEncodedIV ivHex,"hex"
crypt.InitialCount = 42
Dim keyHex As String
keyHex = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0"
crypt.SetEncodedKey keyHex,"hex"

Dim plainText As String
plainText = "The quick brown fox jumped over the lazy dog." + EndOfLine.Windows

Dim stream As New Chilkat.Stream

// We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
Dim eStrings As New Chilkat.StringArray

// Start a background task that will encrypt a stream.
Dim task As Chilkat.Task
task = crypt.EncryptStreamAsync(stream)
Dim success As Boolean
success = task.Run()

// Write plainText to the stream, and read chacha20 encrypted text..
Dim cipherText As String
Dim i As Int32
For i = 1 To 10
    // Note: An encryption algorithm's block size will cause buffering,
    // and therefore not every loop iteration will produce output.
    success = stream.WriteString(plainText)
    If (stream.DataAvailable = True) Then
        cipherText = stream.ReadBytesENC("hex")
        System.DebugLog(cipherText)
        success = eStrings.Append(cipherText)
    End If

Next

// Tell the background task that the stream has ended.
success = stream.WriteClose()

// Let's make sure the background task finished.
// It should already be the case that the task is finished.
While (task.Finished <> True)
    task.SleepMs 20
Wend

// Get any remaining data available from the stream.
If (stream.DataAvailable = True) Then
    cipherText = stream.ReadBytesENC("hex")
    System.DebugLog(cipherText)
    success = eStrings.Append(cipherText)
End If

If (task.TaskSuccess <> True) Then
    System.DebugLog("async encryption failed:")
    System.DebugLog(task.ResultErrorText)
    success = False
End If

System.DebugLog("-- encrypt finished --")

// Now decrypt to return the original.

// Reset the stream object so it can be used again.
stream.Reset 

// Start a background task that will decrypt a stream.
task = crypt.DecryptStreamAsync(stream)
success = task.Run()

Dim n As Int32
n = eStrings.Count
For i = 0 To n - 1
    success = stream.WriteBytesENC(eStrings.GetString(i),"hex")
    If (stream.DataAvailable = True) Then
        plainText = stream.ReadString()
        System.DebugLog(plainText)
    End If

Next

// Tell the background task that the stream has ended.
success = stream.WriteClose()

// Let's make sure the background task finished.
// It should already be the case that the task is finished.
While (task.Finished <> True)
    task.SleepMs 20
Wend

// Get any remaining data available from the stream.
If (stream.DataAvailable = True) Then
    plainText = stream.ReadString()
    System.DebugLog(plainText)
End If

If (task.TaskSuccess <> True) Then
    System.DebugLog("async decryption failed:")
    System.DebugLog(task.ResultErrorText)
    success = False
End If

System.DebugLog("-- decrypt finished --")